Vibrio vulnificus and Vibrio cholerae are small organisms called bacteria that live in the marine environment. Vibrio cholerae can also survive in fresh water. By drinking water, eating fruits and vegetables, fish or shellfish that are contaminated with this bacterium (one bacteria), a person can become very ill or may even die from the disease cholera which causes severe diarrhea and dehydration. Vibrio vulnificus can cause serious illness and even death within three days in people who eat raw or improperly cooked fish or shellfish that are infected with this microorganism.
There are many types of bacteria, both good and bad, in food and water. To find out whether water or food contains these harmful Vibrio bacteria, or if a person is infected with them, laboratory tests must be performed. The first step is to culture, or grow, the bacteria in a special liquid. Then a series of tests are done to identify the bacteria based on whether or not they use certain sugars and other compounds in order to grow. It may take as long as one week to do these tests and by that time a person may die if not given the proper medicine. What is needed is a rapid and easy way to detect and identify Vibrio cholerae and Vibrio vulnificus.
A faster way to check for the presence of these bacteria is to use a molecule called an antibody that recognizes then binds to a specific part of the bacterium. See, for example, Tamplin, M. L. et al.: Applied and Environmental Microbiology, 57:1235-1240 (April 1991), which reports an enzyme immunoassay for the identification of Vibrio vulnificus in seawater, sediment and oysters. However, this method also requires growing the bacteria first and still takes several days to do. Also, antibodies may be too specific and detect only those bacteria from one source but not from another.
Another method involves the use of a "gene probe" to identify the bacteria. Every living organism has molecules of DNA (deoxyribonucleic acid) which contains instructions for each cell to make the things it needs to sustain life. A gene is a piece of DNA that instructs the cell to make one particular type of protein molecule. A gene probe is also made of DNA. See, for example, Amann, R. et al.: Nature. 351:161-164 (May 9, 1991); and Amann, R. et al.: J. Bacteriology. 173:762-770 (February 1990).
Vibrio vulnificus and Vibrio cholerae have specific genes that make proteins which are responsible for causing sickness. A gene probe that specifically seeks out the genes for these toxic proteins can be used to find out whether these bacteria are in food, water or people. However, there is a problem with using a gene probe. Bacteria are one-celled organisms. Each bacterium has only one gene for each kind of protein it makes. It is difficult to detect the one and only toxic protein gene in each cell.
One way to solve this problem is to use a method called PCR to amplify (make many copies of) the gene in a test tube and then use the gene probe to find the gene copies. This method, however, is sophisticated and time-consuming and requires a sufficient number of bacteria to perform the method.
With the current outbreak of Vibrio cholerae in South America, it is apparent that a rapid means of detection is warranted. Consequently, there is a need in the industry for simple, but quick and accurate tests for the reliable and early detection of the bacteria Vibrio vulnificus or Vibrio cholerae in, for example, water, food, blood, feces, and the like, contaminated with such bateria.